1. Field of the Invention
The present invention relates to expansion joint covers. More particularly, the present invention relates to a roof joint cover that accommodates expansion, contraction, shear, and rotational movement between two surfaces.
2. Description of Prior Art
Buildings are typically constructed of rigid materials such as concrete and steel which are chosen for their ability to support loads and resist movement under those loads. Unfortunately, such rigid materials sometimes experience failures when they expand or contract due to changing temperatures or when they move due to seismic events.
To prevent failures, it is common practice to build expansion joints into buildings. Expansion joints are essentially gaps between two rigid surfaces of a building which allow the two surfaces to move with respect to each other without the failures described above.
Typically, an expansion joint is either filled, covered, or both. An expansion joint can be filled with a flexible material with desired characteristics such that it is, for example, waterproof and/or fire resistant. While the flexible material may effectively seal the expansion joint, it is typically not aesthetically appealing and therefore is often covered.
Several prior art expansion joint cover designs are commonly used. Some cover designs incorporate a plate which is secured to one of two surfaces to span an expansion joint between the two surfaces. An end of the plate typically slides against the other surface in order to accommodate variations in expansion and contraction. Unfortunately, these designs cannot effectively accommodate variations in sheer and torsion between the two surfaces.
Another prior art design includes a plate that slides within at least one housing. The housing is secured to one of two surfaces of an expansion joint. The plate is secured to the other surface. The plate slides within the housing in order to accommodate variations in expansion and contraction. However, the internal dimensions of the housing limit the allowable shear and torsion between the two surfaces.
Another prior art design includes a plate with a first end connected to one of two surfaces of an expansion joint by a hinge. A second end of the plate slides within a housing, which is fixedly mounted to the other surface. The plate is thus able to accommodate variations in expansion and separation between the two surfaces. The hinge is able to accommodate variations in torsion between the two surfaces. However, the internal dimensions of the housing still limit allowable shear between the two surfaces.
Accordingly, there is a need for an improved expansion joint cover that overcomes the limitations of the prior art. Specifically, there is a need for an improved roof joint cover that can accommodate variations in expansion, contraction, shear, and torsion between two surfaces of an expansion joint.